Site-specific vibrational dynamics of the CD3ζ membrane peptide using heterodyned two-dimensional infrared photon echo spectroscopy

The amide I vibrational dynamics of a 27 residue peptide in lipid vesicles that encompasses the transmembrane domain of the T-cell receptor CD3 ζ was studied using a heterodyned two-dimensional (2D IR) infrered spectroscopy. The amide I mode of the 49-Leucine residue was spectroscopically isolated using 1- ¹³C= ¹⁸O isotope labeling. The homogeneous and inhomogeneous linewidths of this mode was measured by fitting the 2D IR spectrum collected with a photon echo pulse sequence. The population relaxation time of the amide I band was also measured with a transient grating, which was found to contribute 9 cm ^-1 to the linewidth.